At least 19 tornadoes struck yesterday, destroying homes and businesses, injuring at least eight people and knocking out power to hundreds of thousands.

That was just “the beginning of a multi-day catastrophic and potentially historic heavy rainfall event”, the NWS said.

Arkansas, Missouri, Tennessee and Mississippi faced the threat of a “generational flood event” with some locations forecast to see as much as 38cm of rain by the weekend, which could cause rivers to burst their banks.

No fatalities were reported as of early today.

Four people were injured in Craighead County in Arkansas, and four others, including one critically, were injured when a church was hit in Ballard County, Kentucky, according to local officials.

Railroad company BNSF said it had received a report of a freight train derailment near the storm-hit city of Bay in Arkansas, without specifying the cause.

Late Wednesday, Arkansas, Kentucky and Tennessee declared a state of emergency.

The national weather service said parts of Arkansas, Missouri, Indiana, Illinois, Ohio and Texas were under a high risk of severe thunderstorms today, warning of more tornadoes, hail and life-threatening flooding.

“The word for tonight is ‘chaotic’,” Scott Kleebauer, a NWS meteorologist, said yesterday.

“This is a large expanse of storms migrating slowly to the east, stretching from southeast Michigan down into southeastern Arkansas.”

Missouri’s emergency management agency said a tornado that hit the town of Nevada, Missouri, had caused “major damage to several businesses, power poles were snapped and several (empty) train cars were flipped onto their sides by the powerful storm!”

More than 400,000 customers had their power knocked out across the storm-hit area, according to PowerOutage.us.